This application incorporates by reference Taiwanese Application Serial No. 88114439, filed Aug. 24, 1999.
The invention relates in general to a signal switch apparatus, and more particularly to a signal switch apparatus which is utilized to control the interrupt signals of the small computer system interface, SCSI, card and the redundant array of independent disk, RAID, card.
The development of the software is becoming more versatile and user-friendly. However, it results in the requirement of larger memory space. For supplying larger memory space, software is usually stored in a compact disk-read only memory, CD-ROM nowadays. So computer system is usually sold with a CD-ROM drive. Besides, the software is installed in the hard disk drive, HDD. Therefore, a big-storage HDD is needed to install the operation system and other software. The speed of the HDD and its transmission interface are also important for better performance.
Two interface standards of HDD are popular. One is integrated disk electronics, IDE, and the other is small computer system interface, SCSI. The transmission speed of SCSI is faster than that of IDE.
IDE interface standard is established by Compaq co. The HDD controller is integrated into HDD according to IDE. Then, the total cost is decreased. Gradually, the IDE interface standard is applied to many kinds of the peripherals such as the CD-ROM reader. IDE HDD and the IDE CD-ROM reader have become the basic peripherals of the computer.
SCSI standard is established by the American National Standards Institute, ANSI, in 1986. Utilizing the SCSI card, a number of HDD and/or the CD-ROM reader can be connected to a computer system. The SCSI card is usually inserted into the peripheral component interface, PCI, slot.
In order to improve the functions and the speed of SCSI HDD, a redundant array of independent disk, RAID, card has been developed to cooperate with the SCSI card.
Referring to FIG. 1A, when SCSI HDDs, HDD#1, HDD#2, . . . , HDD#8, are accessing data, the interrupt signal is sent by the SCSI card 120 to CPU 110 through the interrupt controller 140. Here, for the sake of illustration, the path of the interrupt signal has been simplified.
Referring to FIG. 1B, the interrupt signal sent by the SCSI card 120 is first transmitted to the RAID card 130, then sends to the interrupt controller 140 and sent to CPU 110. That is, the interrupt signal of SCSI card 120 is not sent to the interrupt controller 140 directly when the RAID card 130 is cooperated.
The RAID card is provided with several operation modes. Among them, mode 0, mode 1, mode 3, and mode 5 are often used.
High data access speed is the characteristic of mode 0. In mode 0, the bandwidth of the SCSI card is shared by HDDs. If the bandwidth of the SCSI card is 80 MB/s and that of one HDD is 20 MB/s, 4 HDDs can access data at the same time. Therefore, in mode 0, a number of HDDs can access data simultaneously through the SCSI card, which is the reason of high data access speed.
In mode 1, the mirror principle is utilized to prevent data from being lost. One of the HDDs is designated to backup data. Whenever data are written into other HDDs, data is backup to the designated HDD. While data stored in any one of the HDDs are lost, the designated HDD can be utilized to recover lost data.
In mode 3, parity bits are utilized to prevent data loss. One HDD is designated to store parity bits. Whenever data are written into other HDDs, the parity bit according to data is stored in the designated HDD. Thus, the speed of data recovering is increased. Mode 3 also has functions of mode 0.
In mode 5, parity bits are utilized to prevent data loss, too. The difference between mode 5 and mode 3 is that one HDD is designated to store parity bits in mode 3, but parity bits are stored in all HDDs in a circulating order in mode 5. Memory space for storing parity bits in each HDD is determined by algorithm. For example, whenever there are data written into HDDs, the respective parity bit is stored in the first HDD. While memory space of the first HDD for storing parity bits is full, the respective parity bit is stored in the second HDD. In this way, parity bits are stored in HDDs in a circulating order. Moreover, mode 5 also has functions of mode 0.
Referring to FIG. 2A, the SCSI card 220 is integrated into the RAID card 210, which is inserted into the PCI slot 240. Then, interrupt signals INTA#xcx9cINTD# of the RAID card 210 are sent to the interrupt controller 230.
Referring to FIG. 2B, the SCSI card 260 is separated from the RAID card 250 and is integrated into the motherboard 200. The RAID card 250 is inserted into the PCI slot 280. When a RAID card is inserted into a PCI slot, the PCI slot is called RAID upgrade bus interface, RUBI, bus. When there is no RAID card inserted into the RUBI bus, the RUBI bus can also be used as a PCI bus. Interrupt signals INTA#xcx9cINTD# are sent to the interrupt controller 270 as shown in FIG. 2B.
However, the above-mentioned two conventional ways of cooperating the RAID card and the SCSI card both have the drawback of high cost of upgrading.
As illustrated in FIG. 2A, the SCSI card 220 is integrated into the RAID card 210. Therefore, when any one of two cards is upgraded, both of two cards have to be upgraded. As a result, the cost of the hardware is high.
Similarly, in FIG. 2B, the SCSI card 260 is integrated into the motherboard 200. Therefore, when the SCSI card is upgraded, the whole motherboard 200 should be upgraded. Obviously, the high cost for upgrading the hardware is unpleasant.
It is therefore an object of the invention to provide a signal switch apparatus that can lower the cost for upgrading the SCSI card or the RAID card. Utilizing the signal switch apparatus, interrupt signals of the SCSI card can be transmitted to the interrupt controller or the RAID card according to different situations.
The invention achieves the above-identified object by providing a signal switch apparatus, which is disposed in a motherboard. The motherboard includes an interrupt controller, and two PCI slots. The signal switch apparatus includes: a signal switch component, which is connected to the interrupt controller, the first PCI slot, and the second PCI slot. When the SCSI card is inserted into the first PCI slot, the interrupt signal sent by the SCSI card is transmitted to the interrupt controller through the signal switch component. When the SCSI card and the RAID card are respectively inserted into the first and the second PCI slots, the interrupt signal sent by the SCSI card is transmitted to the RAID card.